1. Field of the Invention
The present invention relates to an air conditioning system provided with a device for detecting leakage of refrigerant from a heat exchanger, such as an evaporator, arranged in a chamber to be subjected to an air conditioning. The present invention is particularly suitable for an air conditioning system wherein, as a refrigerant, a combustible fluid, such as propane or butane, or a toxic fluid such as a carbon dioxide or ammonia, is employed.
2. Description of Related Art
An air conditioning system which is provided with means for preventing a refrigerant from leaking is shown, for example, in the Japanese Unexamined Utility Model Publication No. 54-62137. In this prior art, detection of the leakage of the refrigerant is done based on a pressure change at the high pressure side of the refrigerating system constructing the air conditioning system.
In such an air conditioning system utilizing, as the refrigerant, a combustible fluid or carbon dioxide, it is necessary that any leakage of the refrigerant from heat exchanging parts in the cabin, such as an evaporator, is detected very quickly. A quick detection of leakage of refrigerant from parts in the cabin cannot, however, be executed in the prior art since detection of the leakage of the refrigerant, by the pressure change at the high pressure part (condenser) makes it difficult to identify a particular part at which the leakage of the refrigerant is actually occurring.
Japanese Unexamined Utility Model Publication No. 58-54904 discloses a gas sensor, for detecting leakage of a gas, which is arranged in a cabin or an air conditioning apparatus. However, this prior art is, also, disadvantageous in that a quick detection of the leakage of the refrigerant is not possible due to the following reason. Namely, although not described in a detailed manner in the 904 publication, the gas sensor is generally of a contact combustion type, where an existence of a gas is detected in accordance with the degree of an oxidation of the gas to be detected. In this contact combustion type gas sensor, it is necessary to increase the temperature of the sensor part to a temperature which is suitable for an oxidation of the gas and which is in a range between 250 to 300.degree. C. in case of a combustible fluid. Thus, any detection of the existence of the gas, i.e., an occurrence of the leakage of the gas can not be done until the gas temperature is increased to a temperature in the above range.
Furthermore, the location of the gas sensor must be suitably determined while considering various situations such as a difference in the density between the refrigerant and the air and the flow of the air. Namely, a non suitable location of the gas sensor may cause, irrespective of a fact that a leakage of the gas has actually occurred, the sensor to not detect the occurrence of the leakage of the gas in good time.